1. Field of the Invention
The present invention relates to a method of flip-chip mounting and in more detail to a method of flip-chip mounting that can avoid the problem of a semiconductor chip being damaged during bonding due to differences in thermal expansion coefficients between the semiconductor chip and a mounting substrate.
2. Related Art
Among methods of mounting a semiconductor chip on a mounting substrate as a flip-chip, as shown in FIG. 5A, there is a method that connects a semiconductor chip 14 as a flip-chip after applying a resin material 12 in advance onto a semiconductor chip mounting region of a mounting substrate 10. FIG. 5B shows a state where the semiconductor chip 14 is supported by a pressure/heat applying head 20, is positioned with respect to the mounting substrate 10, and is mounted on the mounting substrate 10 while pressure and heat are applied to the semiconductor chip 14.
When the resin material 12 is supplied onto the mounting substrate 10 in advance and the semiconductor chip 14 is connected as a flip-chip, as shown in FIG. 5B, the mounting substrate 10 is supported on a stage 22 that has been heated to around 70 to 80° C., and mounting is carried out after the pressure/heat applying head 20 has been heated to the thermal hardening temperature or higher of the resin material 12 (around 200° C., for example). By merely heating the semiconductor chip 14 for around five seconds using the pressure/heat applying head 20, bumps 14a of the semiconductor chip 14 are electrically connected to connection pads formed on the mounting substrate 10 and the resin material 12 that fills the gap between the semiconductor chip 14 and the mounting substrate 10 is thermally hardened.
Patent Document 1
Japanese Laid-Open Patent Publication No. 2000-138253
Patent Document 2
Japanese Laid-Open Patent Publication No. S57-176738
Patent Document 3
Japanese Laid-Open Patent Publication No. 2000-299330
Patent Document 4
Japanese Laid-Open Patent Publication No. 2000-323523
However, since the thermal expansion coefficients of the semiconductor chip 14 and the mounting substrate 10 that is made of resin differ by a factor of around three, when the semiconductor chip 14 is flip-chip mounted, due to the large difference in thermal expansion between the semiconductor chip 14 and the mounting substrate 10, after mounting, as shown in FIG. 6, the mounting substrate 10 becomes warped toward the semiconductor chip 14.
If mounting is carried out with the mounting substrate 10 in a warped state and the gap between the surfaces of the mounting substrate 10 and the semiconductor chip 14 becomes narrow in a central part of the chip mounting surface of the mounting substrate 10, filler such as alumina or silica added to the resin material 12 to make the thermal expansion coefficient match that of the semiconductor chip 14 is compressed by the mounting substrate 10 and the semiconductor chip 14, resulting in the problem of damage to the circuit surface of the semiconductor chip 14 and in wiring formed on the circuit surface becoming disconnected.
When the bumps 14a are formed on the semiconductor chip 14 at wide intervals, it is possible to form large, high bumps 14a, and therefore even if the mounting substrate 10 becomes warped during flip-chip bonding, the problem of the semiconductor chip 14 being damaged hardly occurs. However, with a product where the bumps 14a are disposed with a high density, the bumps 14a themselves become small and the height of the bumps 14a becomes lower (around 15 μm), and therefore there is the problem that the semiconductor chip 14 can be damaged even if the mounting substrate 10 only becomes slightly warped.